M6 PM Fate and Transport of Pollutants from Dredging and Placement|
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 324-326
142 (RAV-1116-538296) Volatile Emissions from Sediment and Dredged Material Suspensions during Remediation.
Start time: 1:50 PM
Ravikrishna, R1, Valsaraj, K1, Price, C2, Thibodeaux, L1, 1 Gordon A. & Mary Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA, USA2 US Army ERDC, Environmental Laboratory, Vicksburg, MS, USA
Resuspension of contaminated sediments can occur during dredging and from dredged material slurries in a CDF during the filling stage. Preliminary laboratory data has shown that volatilization of chemicals from solids suspension resulting from dredging and CDF activities is a significant pathway for contaminant release. Mathematical models are required to predict the extent of evaporative releases from various scenario of sediment and dredged material suspension. Experimental data from laboratory and field studies are necessary to validate these models for incorporation into a risk assessment framework. Laboratory experiments were conducted with Indiana harbor Canal dredged material to simulate various scenarios of resuspension in an oscillating grid flux chamber. Air emission fluxes, aqueous phase chemical and solid concentrations were measured as a function of time. Comparisons with a mathematical model is presented and the effectiveness of this model will be discussed.
143 (KEI-1117-741152) Confined Disposal Facility Evaluations using Uplands Testing Manual.
Start time: 2:10 PM
Keil, K1, 1 US Army Corps of Engineers, Buffalo District, Buffalo, NY, USA
Contaminant monitoring assessments are underway in order to determine whether or not further management actions need to be taken at the Federal dredged material confined disposal facilities (CDFs) within the Buffalo District, US Army Corps of Engineers, in order to ensure protection of human health and the environment. Management actions would be recommended if it is determined that contaminants are migrating from dredged material within the CDF into the environment outside the facility at levels that would pose a risk to human health or the environment. These evaluations follow guidance contained in the Evaluation of Dredged Material Proposed for Disposal at Island, Nearshore, or Upland Confined Dsposal Facilities Testing Manual (UTM) (USACE 2003), and involve successive tiers of assessment. The UTM uses a risk-based approach in which potential contaminant migration pathways are identified. The migration pathways are routes by which contaminants or constituents of potential concern associated with dredged material within the CDF may move from the dredged material into the environment outside the facility. Secondly, environmental or human receptors are identified. These receptors have the potential to be exposed to contaminants associated with the dredged material inside the CDF, once these contaminants migrate outside the facility. Thirdly, risk-based screening levels are identified that are protective of the identified receptors that could be exposed via the identified migration pathways. In the first tier of the evaluation, concentrations of constituents in the dredged material are compared to the risk-based criteria. If screening levels are exceeded, then additional tiers of analysis may be warranted. The additional tiered evaluations include further modeling, or laboratory or field based testing. If further modeling and testing still indicates a potential ffor risk, then the final tier in this evaluation is a site-specific risk assessment.
144 (ZAH-1118-072753) Quantifying the Fate of Organic Contaminants Released due to Dredging Operations.
Start time: 2:30 PM
Zahakos, H1, 1 Quantitative Environmental Analysis, LLC, Montvale, NJ, USA
The dispersal of contaminated sediments during dredging operations is a major concern. Material lost to the water column has the potential to adversely impact water quality and aquatic life over a much broader area than the immediate vicinity of the dredging operation. Hydrodynamic conditions and sediment properties determine the fate of resuspended sediments and particulate-bound contaminants. Contaminant desorption during resuspension results in greater dispersal and bioavailability of contaminants. Conventional fate models assume equilibrium partitioning between sorbed and aqueous phases. This is often adequate to assess long-term contaminant fate, for example as part of remedial investigations. During dredging resuspension and redeposition, however, short time scales dominate. This can invalidate the equilibrium assumption. A new mechanistic modeling framework has been developed. This model integrates laboratory studies on contaminant sorption/desorption dynamics with hydrodynamic and sediment transport processes that affect contaminant fate from dredge losses. The model accommodates multiple sediment classes and desorption rates. Simulations illustrate the importance of local hydrodynamic conditions and sediment properties on the fate and bioavailability of contaminants.
145 (THI-1117-836771) PAH volatile emissions from dredged material 2-Model development and interpretation.
Start time: 2:50 PM
thibodeaux, l 1, fountain, k1, price, c2, ravikrishna, r1, valsaraj, k1, 1 louisiana state university2 us army corp of engineers
Based on measured PAH chemical fluxes to air data obtained from a pilot-scale size windtunnel containing dredged material(DM)the current state of the art mathematical model used for predicting emissions was re-formulated. A process involving the co-evaporation of water and its effect which changed the physics of the soil surface needed to be included. Based on the windtunnel fluxes three regimes are identified to describe the water dominated evaporation process. Early during the experiment, Regime-1, a standing water layer covers the soil-like DM surface and low to zero chemical flux occurs. In Regime-2 dry soil with less water(i.e., "dry patches")occurs with increasing time, producing rapidly increasing fluxes. A maximum flux occurs at complete dryness. Afterwards Regime-3 is characterized by slowly decreasing fluxes. The key factor in restructuring the model was to include the water evaporation/dry soil patch formtion process of Regime-2. A time-linear patch growth area functon was adopted which is consistent with the well known constant rate-period used for water evavpration from porous solids(It normally proceeds the well known falling-rate evaporation period.). Time duration of the constant-rate period is the one adjustable parameter added to the original model. Upon implementing the modified model it was discovered that the chemical evaporation process occuring during Regime-2 was controlled by and sensative to the numerical magnitude of the air-side mass-transfer coefficient. Careful adjustment of this coefficient within the range of values consistent with wind tunnel operations allowed good model-vs-data fitting during Regime-2. Interestingly, the soil-side resistance process dominates the magnitude and shape of the decreasing flux-vs-time data for Regime-3. Regime-1 was not modeled; it presence in the data sets was an artifact of the windtunnel operation and so is not characteristic of field operations for which the model is being developed. The presentation will conclude with a discussion on using the model for making field emission estimates from DM placed in confined disposal facilities.
Start time: 3:10 PM
146 (THI-1117-833308) PAH volatile emissions from dredged material-1. Windtunnel measurements and results.
Start time: 3:50 PM
thibodeaux, l1, fountain, k1, price, c2, ravikrishna, r1, valsaraj, k1, 1 louisiana state university2 us army corp of engineers
Flux measurements to air were made on naphthalene, methyl naphthalene and phenanthrene using 2.3 cubic meters of dredged material from Indiana Harbor and Canal, Chicago Il. The DM was extracted by a mechanical dredge, placed in drum containers, shipped and held in a refrigerated truck prior to mixing and placement in the pilot-scale size windtunnel. Atmospheric air at ambient temoeratures and humidities was drawn through the device. Three experiments were performed over a three month period from November '03 to January '04. Re-working and re-watering was done between experiments. The windtunnel was a rectangular shaped box positioned above a 1.2 meter wide by 4.6 meter long lysimeter. A constant 1.2 m/s(2.6 mi/hr) wind speed was maintained. The soil loadings were 2.7, 1.2 and 4.3 mg/kg dry for NAPH, M-NAPH and PHEN respectively. The maximum fluxes observed were 50, 25 2.0 ng/sq cm/hour respectively. They occured several hours into the experimental runs! All three chemicals displayed this very unusual flux-vs-time pattern. Numerous previous flux experiments using small laboratory-scale size evaporation surfaces all displayed the maximum flux at time zero followed by a decreasing flux which decayed exponentially with time. Based on water saturation measurements in the windtunnel soil it was concluded that the moisture vs time behavior was key to interpreting the unusual flux pattern. Initially for a short time-period the flux was near zero. This was followed by a dramatic period of increasing flux with increasing time till a maximum was achieved. Afterwards the flux decreased in the usual exponential decay fashion. A 3-regime water dominated process is proposed to explain the flux pattern. During Regime-1 a layer of water or "soupy" fluid mixture covers much of the soil surface. A small flux occurs but quickly disappears because of non detectable concentrations in air. Regime-2 occurs as the surface soil porespaces become progressively air-filled. Volatilization rate increases as these "dry patches" increasingly form on the surface with time. When the entire surface becomes dry, in the sense that all surface porespaces are air filled, the maximun flux occurs. Regime-3 is characterized by decreasing fluxes as chemical depletion occurs in the surface layers slowing the chemical emission process.
147 (GAR-1117-807215) Assessment of Leaching Potential of Metals from Contaminated Sediments Placed in Upland Environments.
Start time: 4:10 PM
Gardner, K1, Tsiatsios, C1, Melton, J1, 1 University of New Hampshire, Durham, NH, USA
This research focused on the leaching characteristics of metals from NY/NJ Harbor sediments. Sediments were evaluated as fill materials in an as-is state and with the addition of 7% dry Portland cement to 93% wet dredged material which created a suitable controlled low strength material (also called flowable-fill) product. Contaminant release estimates and mass flux rates were evaluated using pH-dependent leaching, liquid-to-solid ratio dependent leaching and column leaching. A simple percolation model and the EPA Industrial Waste Management Evaluation Model (IWEM) were used to evaluate the release of metals into the groundwater at a theoretical site using parameters from the Bark Camp Mine site in Pennsylvania. Results showed that the stabilization of contaminated sediments with Portland cement reduces the leachability of metals at pH values greater than 9, but does not affect release at pH values less than 9 for As, Cd, Cr, Cu, Ni and Pb. The flowable fill material has a natural pH of 11.2-12.2 with a high buffering capacity. Under acid rain percolation conditions, the flowable fill would be expected to remain above a pH 9 for approximately 10,000 years. The estimated concentration of metals leached during a 100-year time interval for the as-is sediment and flowable fill material averaged 23.6% and 4.4% of the total metals, respectively. The flux and IWEM results showed a decrease in the mass rate of transfer and groundwater metal concentrations after stabilization in the flowable fill matrix for As, Cd, Cr, Ni, Pb and Zn, respectively. Cu has a greater release after stabilization due to complexation with dissolved organic carbon released at the high pH of the flowable fill matrix. IWEM was found to be a useful modeling context to consider the environmental impact of fills using sediments.
148 (TRA-1117-851911) Remediation Dredging Feasibiliy Study for Philadelphia Naval Business Center Navy Reserve Basin (Philadelphia Shipyard).
Start time: 4:30 PM
Tracey, G1, Allen, B1, Poucher, S1, Barclift, D2, Speicher, J2, Stillman, M1, 1 Science Applications International Corporation, Newport, RI2 US Navy Engineering Field Activity Northeast, Lester, PA
The Navy is embarking on a large (up to 600,000 cy) dredging project to deepen PNBC Reserve Basin for navigation dredging and sediment remediation purposes. In the present study, a three phased approach was implemented to collect and evaluate a wide range of information for purposes of supporting the sediment remediation Feasibility Study. In Phase I, Preliminary Remediation Goals (PRGs) that had been previously developed were further evaluated to ensure that the necessary CoCs and associated concentrations that will be remediated are sufficient and protective of ecological and human health risks. Accordingly, issues regarding pollutant transport, chemical partitioning, bioavailability and regional background concentrations were investigated. In Phase II, questions regarding the long term effectiveness of remediation were investigated including factors such as contaminant source control, hydrodynamics and water quality that may limit the recovery of the system after dredging is complete. Finally, in Phase III, additional information on sediment removal and disposal options was collected in terms of volume, treatability (dewatering and engineering characteristics) and specific removal issues (i.e., sediments near wharfs) which may greatly affect the logistics of the remediation process. A number of key conclusions have been reached on the basis of the individual studies and assessments. Taken together, the results indicate that the proper PRGs have been developed and recontamination after dredging is not likely to occur. The results of these studies as well as the range of potential remedial options under consideration will be presented.
149 (PRI-1117-838799) Predicting Water Quality Compliance for the Discharge of Runoff Water from Dredged Material.
Start time: 4:50 PM
Price, R1, 1 USAERDC - Environmental Laboratory, Vicksburg, MS, USA
Placement of dredged material into a confined disposal facility (CDF) may result in discharge of surface runoff water during rainfall. Water leaving an upland confined disposal facility (CDF) must meet applicable State water quality standards for discharge into receiving waters. When dredged material is placed in a CDF, contaminant movement from the wet, unoxidized material will be mainly associated with suspended solids. As the material dries and oxidizes, suspended solids concentration may decrease while contaminants such as heavy metals may become more soluble due to physicochemical changes of the dredged material. A rapid screening test was developed to predict the effects of these changes on the resulting water quality discharge so that controls could be engineered into the CDF design process. The simplified laboratory runoff procedure (SLRP) simulates the oxidative processes that may have significant effect on pH and solubility of metals. Sediment samples are collected from a proposed dredging project and oxidized with 30% H2O2. Oxidized sediment is added to deionized water to simulate 50, 500 and 5000 mg l-1 total suspended solids (TSS). These TSS concentrations are within the range measured in runoff water from aged dredged material in CDFs. To simulate freshly placed dredged material, unoxided sediment is used at 500, 5,000 and 50,000 mg l-1. The prepared samples are placed on a mechanical shaker and agitated for one hour to ensure complete particle suspension. Samples are then analyzed for both total and soluble (filtered) contaminants. Results of field and laboratory studies will be presented.
150 (GAR-1117-807761) Colloid- and DOC-facilitated Leaching of Metals from Contaminated Estuarine Sediments in Freshwater Upland Environments.
Start time: 5:10 PM
Gardner, K1, Tsiatsios, C1, 1 University of New Hampshire, Durham, NH, USA
This research focused on the leaching characteristics of metals from NY/NJ Harbor and New Bedford Harbor sediments. Contaminant release estimates and mass flux rates were evaluated using batch tests and column leaching tests. Column leaching tests were conducted to quantify the significance of colloid-facilitated transport of metals from estuarine sediments being managed in freshwater environments. Colloidal release occurred after the high ionic strength pore water was washed-out by low ionic strength eluent, which mimicked rainfall infiltration into a CDF or similar fill application. Leachate dissolved organic carbon (DOC) and metal elution trends were similar. It was found that metals associated with DOC and not with larger turbidity-causing particulates (>0.02 micrometer). Visual MINTEQ modeling indicated a strong metal-DOC relationship with the complexed species accounting for an average percent of total dissolved concentration of 89.8% and 99.5% at 5.5 and 30 pore volumes, respectively. This suggests the metals were complexed with DOC, which facilitated the transport of contaminants from the estuarine sediments. The results from the LS ratio dependent batch tests and column leaching tests were compared to determine if the batch tests adequately describe the leaching behavior of metals from sediment over time. In general, there was good agreement (less than one order of magnitude) at low LS ratios but the accuracy of the predicted metal leachate concentrations decreased at high LS ratios (>5mL/g). It seems that the column tests do capture some phenomena not observed in batch leaching tests, particularly the release of DOC and associated metals.